1. Field of the Invention
This invention relates to devices for igniting combustible waste gases and more particularly, to a pilotless flare ignitor which utilizes a timed spark for igniting waste gas issuing from a flare stack. In a preferred embodiment the pilotless flare ignitor is characterized by an ignitor housing including a horizontal ignitor head having an open end which extends through an opening provided in the flare stack. A pair of parallel electrodes are mounted in the ignitor head, the ends of which electrodes are angled to define a diagonal spark gap in which a timed spark is periodically or intermittently generated by means of a timer-controlled, step-up transformer wired to the electrodes. As the waste gas flows upwardly through the flare stack and into the open end of the ignitor head, the timer is operated in a preselected on-off sequence to energize the generator and the spark ignites the waste gas in the ignitor head and flare stack. After the spark is extinguished, the flaming gas is cleared from within the ignitor head and confined essentially to that segment of the flame stack located above the ignitor head, to minimize corrosion of the ignitor head by the burning gas.
Natural gas or methane is often found with deposits of petroleum. When the gas occurs in quantities which are too small for economical transportation to a point of use, the gas is considered waste gas and disposed of in the most convenient manner. For example, in oil drilling operations, natural gas frequently becomes mixed with the packing mud in the drill hole. The mud is passed through a mud-gas separator and the major portion of the mud re-circulated to the drill hole, while the gas is expelled through a vertical flare pipe. Whereas in earlier times the gas was simply vented into the atmosphere, current safety regulations generally require the waste gas, which typically contains entrained liquid hydrocarbons, to be burned or flared in order to prevent fire and explosion hazards.
2. Description of the Prior Art
Various arrangements have been devised for the ignition of combustible waste gases vented through vertical flare stacks. Originally, methods of igniting the waste gas included shooting flaming arrows, tracer bullets or signal-type flares through the gas emanating from the flare pipe. However, these practices were unreliable at best and often proved dangerous to humans or livestock in the area of the stack. Another method of igniting the gas included burning an open container of liquid fuel, such as diesel fuel, near the flare pipe outlet. However, the burning diesel fuel was often extinguished by wind or rain, and reignition of the fuel in the presence of accumulating gas was extremely hazardous. Still another method included igniting the gas by an electric spark using an automobile spark coil, electric fence charger or other type of transformer, but since the electrode elements in these applications were placed directly in the stream of the burning gas, they were quickly burned or corroded beyond further use. Additionally, the transformers were often damaged, either by the radiant heat of the gas flame or by the flame itself, as it was blown back toward the transformer by the wind.
Conventional waste gas flare ignitors typically utilize a pilot light or spark-generating electrode which is temporarily placed in the stream of the flowing gas to ignite the gas, and then retracted from the burning gas to prevent damage to the pilot light or electrode. Typical of these flare ignitors is the "Waste Gas Flare Ignitor" detailed in U.S. Pat. No. 4,431,402, dated Feb. 14, 1984, to Louis F. Hamilton. The flare ignitor is characterized by a movable pilot structure which burns a stored fuel for a selected period of time in order to ignite waste gas issuing from a horizontal flare pipe. The ignitor includes a heat shield, behind which the pilot structure is withdrawn after ignition of the gas, for protection from the heat of the burning gas. Another flare ignitor is the STACKKATCH (trademark) "Hot Rod", manufactured by the Stackmatch Flare Ignition Corporation of Plano, Texas. The flare ignitor is characterized by a pilot gas conduit or pipe which is hingedly and vertically mounted on the flare stack and terminated by a series of pilot openings located between a pair of circular plates provided on the upper end of the pipe. As the pilot gas is distributed upwardly through the pipe and ignited by an electronic pilot generator located inside the pipe adjacent to the pilot openings, the plates are positioned partially over the outlet of the flare stack and the issuing gas ignited, after which the flare ignitor is pivoted away from the stream of burning gas. Still another flare ignitor is manufactured by Flare Industries, Inc., of Austin, Tex. The flare ignitor is characterized by an electronic ignitor head which produces a spark for igniting the waste gas and is mounted on the upper end of a support rod pivotally and vertically mounted on the flare stack. The ignitor head is extended through an opening provided in a wind deflector mounted on the outlet of the flare stack for igniting the issuing waste gas, after which the support rod is pivoted on the flare stack to remove the ignitor head from the stream of burning gas.
An object of this invention is to provide a new and improved, non-pivotable and pilotless flare ignitor for igniting waste gas issuing from a flare stack.
Another object of this invention is to provide a pilotless flare ignitor which transiently produces a spark inside a housing for igniting waste gas issuing from the outlet of a vertical flare stack, wherein the flaming waste gas is essentially confined to that portion of the flare stack extending above the flare ignitor after the spark is extinguished, in order to prevent damage or corrosion of the flare ignitor by the flaming gas.
Still another object of this invention is to provide a non-pivoting, pilotless flare ignitor characterized by an ignitor housing having an open end which extends into a flare stack, within which housing is contained a pair of electrodes defining an angularly-oriented or diagonal spark gap, in which a spark is intermittently generated by means of a timer-controlled, step-up transformer wired to the electrodes, for periodically generating a spark of controlled duration in the spark gap in order to ignite the waste gas issuing from the flare stack. After the spark is extinguished, the flaming gas is cleared from the ignitor housing and confined to that portion of the flare stack extending above the housing to prevent excessive burning or corrosion of the flare ignitor by the flaming gas.